What happened
On August 8, 2020, at approximately 13:15 UTC, a Schempp Hirth Nimbus4DM motorglider was performing a non-commercial cross-country flight. The aircraft had departed from the Goetsenhoeven-Tienen airfield with the intention of flying a three-hour route over the Ardennes. During the approach phase, the aircraft was observed flying a non-standard circuit for runway 06. Witnesses noted that while performing a right-hand turn toward the final approach, the aircraft entered a steep bank, with the wings appearing nearly vertical. Following this maneuver, the aircraft entered a near-vertical dive and struck the ground. The impact was so severe that the aircraft was destroyed, and the two fatalities occurred instantly.
The investigation
Investigators from the AAIU(Be) examined wreckage, analyzed radar recordings, reviewed CCTV footage, and studied flight logger data and witness accounts. Post-crash analysis of the two speed indicators recovered from the site revealed an airspeed of 260 km/h at the moment of impact. While the aircraft did not suffer a structural breakup prior to hitting the ground, examination of the wreckage and wing components showed significant upward deformation. The investigation is currently focused on reconstructing the final moments of the flight to determine the extent of deformation in the flight control rods and wings, specifically to assess if the aircraft's state was recoverable.
Findings
Data confirms that the final right-hand turn toward runway 06 was executed at an airspeed exceeding the maneuvering speed (Va) and at a steep bank angle of approximately 60 degrees. While these flight conditions do not inherently cause a maximum load factor exceedance, the investigation found that a small pitch-up maneuver, whether intentional or caused by a gust of wind, could have easily triggered a structural overstress. Such an event would have resulted in an aircraft upset and subsequent loss of control.